Swarm communication method and device

ABSTRACT

A swarm communication system. Each of a plurality of transceivers determines a transmission cycle duration, and transmits one packet per transmission cycle, each packet being transmitted at a random point in time within the transmission cycle. The duration of the transmission cycle of a first transceiver may be adjusted according to the number of other transceivers within range of the first transceiver, or according to the number of other transmitters within range of each of the other transmitters that are within range of the first transceiver.

CROSS-REFERENCE TO RELATED APPLICATION(S)

The present application claims priority to and the benefit of U.S.Provisional Application No. 62/409,808, filed Oct. 18, 2016, entitled“SELF-OPTIMIZING SWARM COMMUNICATION METHOD AND DEVICE”, the entirecontent of which is incorporated herein by reference.

The present application is related to U.S. patent application Ser. No.14/792,359, filed on Jul. 6, 2015, entitled “RECONFIGURABLE DRIFTMEASUREMENT TOOL”, (“the '359 Application”), the entire content of whichis incorporated herein by reference.

The present application is related to U.S. patent application Ser. No.15/260,224, filed on Sep. 8, 2016, entitled “SWARM AUTOPILOT”, (“the'224 Application”), the entire content of which is incorporated hereinby reference.

FIELD

One or more aspects of embodiments according to the present inventionrelate to communications, and more particularly to a scalable system forcommunication over limited-range communications links betweentransceivers of a collection of transceivers.

BACKGROUND

Swarm robotics is an emerging technology field in which populations ofautonomous agents coordinate their behavior through a distributedalgorithmic architecture. In such swarms, there is a need for a robust,easily implementable, rapidly adaptive communication method that canaccommodate the dense, complex and range-limited nature of robotic swarmcommunication. Specifically, the challenges of scalability, throughput,management, and monitoring are germane in the design or selection of acommunication system for a swarm.

Scalability relates to the ability of the system to accommodate swarmswith large numbers of agents. A swarm may consist of only a few agents,or of several hundred agents or more. A swarm may be an open systemwhere the size of a swarm may quickly change as agents are added orremoved while the swarm is operating. In such a situation it may beadvantageous for the communication system not to rely onpre-coordination of agents. Furthermore, as the size of a swarm changesthe appropriate rate for inter-agent communication may change, and itmay be advantageous for agents to be able to self-adapt as the swarmsize changes.

Throughput relates to the rate at which data can be transmitted betweenone agent and another or the total rate at which data is transmittedbetween agents in the swarm; the latter quantity may be referred to as“total throughput”. Various combinations of signal attenuation and radiointerference may limit the successful transmission of signals. As such,it may be advantageous for the communication system to beself-adjusting, e.g., continually adapting to achieve high throughput asthe swarm reconfigures.

Management refers to control of the swarm by an operator. If agents in aswarm only communicate over short distances it may be challenging for anoperator to manage the entire group, especially agents that are out ofdirect communication. As such, it may be advantageous for thecommunication system to enable the reliable dissemination of groupcommands and the creation of group-scale coherent behavior.

Monitoring refers to the ability of an operator to obtain informationabout the status and activity of the agents in the swarm. If the radiosignals that the agents broadcast are only intended for short-distancecommunication with close neighbors, it may be challenging for anoperator outside a swarm to efficiently monitor the activity of all theagents.

Existing technologies may be poorly suited for deployment in largeswarms that may freely reconfigure, and in which it is advantageous tobe able to add or remove vehicles without pre-planning and withoutdisrupting the communication integrity of the swarm.

Thus, there is a need for an improved communication system for a swarmof agents.

SUMMARY

Aspects of embodiments of the present disclosure are directed toward aswarm communication system. Each of a plurality of transceiversdetermines a transmission cycle duration, and transmits one packet pertransmission cycle, each packet being transmitted at a random point intime within the transmission cycle. The duration of the transmissioncycle of a first transceiver may be adjusted according to the number ofother transceivers within range of the first transceiver, or accordingto the number of other transceivers within range of each of the othertransceivers that are within range of the first transceiver.

According to an embodiment of the present invention there is provided amethod for communicating between a plurality of transceivers, the methodincluding: establishing, by a first transceiver of the plurality oftransceivers, a first transmission cycle interval having a duration; andtransmitting, during the first transmission cycle interval, by the firsttransceiver, a packet, the position in time of the packet within thefirst transmission cycle interval being randomly selected, theestablishing of the first transmission cycle interval includingselecting the duration of the first transmission cycle interval basedon: for each of a plurality of second transceivers, a count oftransceivers within communication range of that second transceiver, theplurality of second transceivers being a subset of the plurality oftransceivers, each of the second transceivers being within communicationrange of the first transceiver.

In one embodiment, the method includes determining, by a secondtransceiver of the plurality of second transceivers, the count oftransceivers within communication range of that second transceiver by:during a first time interval having a duration of k transmission cyclesof that second transceiver, k being a whole number greater than 2:receiving a plurality of packets; and adding, to a list of transceiversidentifiers, a received transceiver identifier when the receivedtransceiver identifier is not already in the list, removing, from thelist each transceiver identifier not in any packet of the plurality ofpackets; and counting the number of transceiver identifiers in the list.

In one embodiment, the selecting of the duration of the firsttransmission cycle interval includes calculating the duration of thefirst transmission cycle interval to be proportional to an average, overthe plurality of second transceivers, of the respective count oftransceivers within communication range of each of the secondtransceivers.

In one embodiment, the selecting of the duration of the firsttransmission cycle interval includes calculating the duration D of thefirst transmission cycle interval according to the equation D=N*T/Bwherein N is the average, over the plurality of second transceivers, ofthe respective count of transceivers within communication range of eachof the second transceivers, T is a duration of the packet, and B is aconstant having a value between 0.1 and 4.0.

In one embodiment, the method includes: receiving, by the firsttransceiver, a packet including received stamp data and received modedata, the stamp data being a member of an ordered list; and when thereceived stamp data is later in the ordered list than stored stamp datain the first transceiver, overwriting the stored stamp data with thereceived stamp data, and overwriting stored mode data in the firsttransceiver with the received mode data; and when the received stampdata is not later in the ordered list than the stored stamp data in thefirst transceiver, leaving the stored stamp data and stored mode dataunchanged.

According to an embodiment of the present invention there is provided amethod for communicating between a plurality of transceivers, the methodincluding: establishing, by a first transceiver of the plurality oftransceivers, a first transmission cycle interval having a duration; andtransmitting, during the first transmission cycle interval, by the firsttransceiver, a packet, the position in time of the packet within thefirst transmission cycle interval being randomly selected, theestablishing of the first transmission cycle interval includingselecting the duration of the first transmission cycle interval basedon: a count of transceivers within communication range of the firsttransceiver; or for each of a plurality of second transceivers, a countof transceivers within communication range of that second transceiver,the plurality of second transceivers being a subset of the plurality oftransceivers, each of the second transceivers being within communicationrange of the first transceiver.

In one embodiment, the selecting the duration of the first transmissioncycle interval includes calculating the duration of the firsttransmission cycle interval to be proportional to the count oftransceivers within communication range of the first transceiver.

In one embodiment, the selecting of the duration of the firsttransmission cycle interval includes calculating the duration D of thefirst transmission cycle interval according to the equation D=N*T/Bwherein N is the count of transceivers within communication range of thefirst transceiver, T is a duration of the packet, and B is a constanthaving a value between 0.1 and 4.0.

In one embodiment, the method includes: receiving, by the firsttransceiver, a packet including received stamp data and received modedata, the stamp data being a member of an ordered list; and when thereceived stamp data is later in the ordered list than stored stamp datain the first transceiver, overwriting the stored stamp data with thereceived stamp data, and overwriting stored mode data in the firsttransceiver with the received mode data; and when the received stampdata is not later in the ordered list than the stored stamp data in thefirst transceiver, leaving the stored stamp data and stored mode dataunchanged.

According to an embodiment of the present invention there is provided asystem, including: a plurality of spatially separated agents, each agentincluding a respective transceiver of a corresponding plurality oftransceivers, a first transceiver of the plurality of transceivers beingconfigured to: establish a first transmission cycle interval having aduration; and transmit, during the first transmission cycle interval, bythe first transceiver, a packet, the position in time of the packetwithin the first transmission cycle interval being randomly selected,the establishing of the first transmission cycle interval includingselecting the duration of the first transmission cycle interval basedon: a count of transceivers within communication range of the firsttransceiver; or for each of a plurality of second transceivers, a countof transceivers within communication range of that second transceiver,the plurality of second transceivers being a subset of the plurality oftransceivers, each of the second transceivers being within communicationrange of the first transceiver.

In one embodiment, the system includes determining, by a secondtransceiver of the plurality of second transceivers, the count oftransceivers within communication range of that second transceiver by:during a first time interval having a duration of k transmission cyclesof that second transceiver, k being a whole number greater than 2:receiving a plurality of packets; and adding, to a list of transceiversidentifiers, a received transceiver identifier when the receivedtransceiver identifier is not already in the list, removing, from thelist each transceiver identifier not in any packet of the plurality ofpackets; and counting the number of transceiver identifiers in the list.

In one embodiment, the selecting of the duration of the firsttransmission cycle interval includes calculating the duration of thefirst transmission cycle interval to be proportional to the count oftransceivers within communication range of the first transceiver.

In one embodiment, the selecting of the duration of the firsttransmission cycle interval includes calculating the duration D of thefirst transmission cycle interval according to the equation D=N*T/Bwherein N is the count of transceivers within communication range of thefirst transceiver, T is a duration of the packet, and B is a constanthaving a value between 0.1 and 4.0.

In one embodiment, the selecting of the duration of the firsttransmission cycle interval includes calculating the duration of thefirst transmission cycle interval to be proportional to an average, overthe plurality of second transceivers, of the respective count oftransceivers within communication range of each of the secondtransceivers.

In one embodiment, the selecting of the duration of the firsttransmission cycle interval includes calculating the duration D of thefirst transmission cycle interval according to the equation D=N*T/Bwherein N is the average, over the plurality of second transceivers, ofthe respective count of transceivers within communication range of eachof the second transceivers, T is a duration of the packet, and B is aconstant having a value between 0.1 and 4.0.

In one embodiment, the system includes: receiving, by the firsttransceiver, a packet including received stamp data and received modedata, the stamp data being a member of an ordered list; and when thereceived stamp data is later in the ordered list than stored stamp datain the first transceiver, overwriting the stored stamp data with thereceived stamp data, and overwriting stored mode data in the firsttransceiver with the received mode data; and when the received stampdata is not later in the ordered list than the stored stamp data in thefirst transceiver, leaving the stored stamp data and stored mode dataunchanged.

In one embodiment, the system includes a sniffer including a directionalantenna, having a gain, in one direction, of at least 5 dBi.

According to an embodiment of the present invention there is provided asystem for providing communications to a swarm of vehicles, the systemincluding a plurality of transceivers, a first transceiver of theplurality of transceivers being configured to: be mechanically andelectrically connected to a vehicle; establish a first transmissioncycle interval having a duration; and transmit, during the firsttransmission cycle interval, by the first transceiver, a packet, theposition in time of the packet within the first transmission cycleinterval being randomly selected, the establishing of the firsttransmission cycle interval including selecting the duration of thefirst transmission cycle interval based on: a count of transceiverswithin communication range of the first transceiver; or for each of aplurality of second transceivers, a count of transceivers withincommunication range of that second transceiver, the plurality of secondtransceivers being a subset of the plurality of transceivers, each ofthe second transceivers being within communication range of the firsttransceiver.

In one embodiment, the first transceiver is configured to send, to thevehicle, information about the location of other nearby transceivers ofthe plurality of transceivers.

In one embodiment, the first transceiver is configured to send, to thevehicle, a commanded velocity vector.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features and advantages of the present invention will beappreciated and understood with reference to the specification, claims,and appended drawings wherein:

FIG. 1 is a map view of a distributed group of autonomous boats,according to an embodiment of the present invention;

FIG. 2 is an illustration of a sequence of transmission cycles, eachincluding a transmitted packet, according to an embodiment of thepresent invention;

FIG. 3 shows three transmission cycles, each with a plurality oftransmitted packets, according to an embodiment of the presentinvention;

FIG. 4 is a graph of successful packet rate as a function of localpopulation size, for four different transmission cycle frequencies,according to an embodiment of the present invention;

FIG. 5 is a flowchart of a method for handling command data, accordingto an embodiment of the present invention;

FIG. 6 is a map view of a swarm of agents each maintaining two parametervalues, according to an embodiment of the present invention;

FIG. 7 is a map view of a swarm of agents monitored by a sniffer,according to an embodiment of the present invention;

FIG. 8 is a schematic drawing showing the use of a relay drone with asniffer, according to an embodiment of the present invention; and

FIG. 9 is a block diagram of a swarm device, according to an embodimentof the present invention.

DETAILED DESCRIPTION

The detailed description set forth below in connection with the appendeddrawings is intended as a description of exemplary embodiments of aswarm communication method and device provided in accordance with thepresent invention and is not intended to represent the only forms inwhich the present invention may be constructed or utilized. Thedescription sets forth the features of the present invention inconnection with the illustrated embodiments. It is to be understood,however, that the same or equivalent functions and structures may beaccomplished by different embodiments that are also intended to beencompassed within the spirit and scope of the invention. As denotedelsewhere herein, like element numbers are intended to indicate likeelements or features.

In some embodiments a swarm includes a plurality of agents, such as theboats 110 illustrated in FIG. 1, each including a transceiver (e.g., aradio transceiver) for communicating with other agents and/or otherentities such as an operator. In some embodiments the communicationsystem includes the transceivers and one or more methods of operatingthem to reduce interference and to achieve acceptable throughput. Asused herein, “throughput” is the rate at which one agent receivessuccessful packets from one or more other agents. The number of agentsin the swarm may be referred to as the “size” of the swarm, and the sizeof the region of space (e.g., the area) over which the swarm extends maybe referred to as the “extent” of the swarm. The distance over whichdata may be successfully transmitted from one transceiver to another maydepend on various factors, including the power of the transmitter, thegain of the receiving antenna, the sensitivity of the receiver, and thetransmission loss between the transmitting antenna and the receivingantenna. The transmission loss between the transmitting antenna and thereceiving antenna may be affected by obstacles (e.g., waves, if theagents are vehicles on the surface of a body of water). Two agents maybe said to be within range of each other if signals may be reliablytransmitted between them, in both directions. The extent of the swarmmay be sufficiently great that some of the agents in the swarm may notbe within range of some other agents in the swarm. This circumstance mayboth (i) be an obstacle to communications between widely separatedagents and it may (ii) reduce the impact of interference betweentransmission from different agents in the swarm.

In some embodiments the communication system employs a distributed,de-centralized architecture that may have significant advantages overembodiments relying on central coordination. A distributed,de-centralized architecture may allow the extent of the swarm to be muchlarger than the communication range between agents, and, it may allowagents to rapidly make decisions in response to changes in localconditions, since they are not waiting for remote instructions. Further,such an embodiment may make it possible for the agents of the swarm tofreely reconfigure their relative positions.

Some embodiments provide solutions to one or more swarm communicationschallenges, including, scalability, throughput, management, andmonitoring. In such an embodiment, all agents may monitor the same,single radio channel or frequency. Each agent repeatedly openlybroadcasts its relevant personal information (such as GPS location) in apacket that is small compared to the transmission cycle duration. Thetransmission cycle duration is consistent or slowly changing, e.g., 1second, but within each cycle each agent chooses a random time tobroadcast its packet, which may have a duration (e.g. 2 milliseconds)that is significantly smaller than the transmission cycle duration.

In some embodiments this mode of operation results in relativelyfrequent collisions, i.e., overlapping of signals from two or moredifferent transmitters at any of the receivers, and resulting losses,but it nonetheless provides acceptable decipherable information(throughput) from non-colliding signals. The communications system ofsome embodiments is scalable and does not require that transceivers besynchronized.

The randomization of the packet transmission time within eachtransmission cycle facilitates the calculation of average values foroffered load (number of packets broadcast), throughput (number ofpackets successfully received, i.e., non-colliding or non-overlappingpackets) and channel utilization (fraction of available broadcast timeused), which in turn makes it possible, using a simple method, for eachagent to adjust its own transmission cycle duration in a way thatresults in adequate total throughput, even while the swarm size andextent change.

In some embodiments the communication system includes features thatimprove swarm functionality and management. For example, a “neighborlist”, may be maintained by each agent; the list may include nearbyagents even if a packet is not received from them with every cycle. Asanother example, a “command data” portion of the packet architecture maybe utilized to reliably disseminate global information through theswarm. Further examples include an artificial parameter maintained bythe agents that establishes unified gradients across the group forglobal management, and a monitoring system wherein rapid packettransmissions make it easy for an operator to monitor an entire swarm byquickly scanning with a directional receiving antenna.

In some embodiments, the communication system has four characteristicsthat result in desired capabilities:

1. The data packets have relatively short durations.

2. All broadcasts are open and one-way (i.e., one-to-many, notpeer-to-peer).

3. The data packets are broadcast on a repeating transmission cycle theduration of which may be fixed or relatively slowly varying, and at arandom time within each transmission cycle (referred to in this documentas “cyclic-random” characteristic).

4. Radio range is limited.

For example, in one embodiment, a swarm includes thousands of agents (asmall subset of which is illustrated in FIG. 1), each of which is asmall boat 110. The swarm may be substantially larger than the radiobroadcast range of any individual agent, which may be on the order of150 meters. Each boat 110 detects its geographic location using anonboard Global Positioning System (GPS) receiver. Each boat 110 also isautonomous and able to navigate using an algorithm that plans atrajectory based on the relative position of close neighbors (i.e., itoperates with a swarm algorithm). Each boat 110 has a transceiver (e.g.,a 2.4 GHz radio) for sending and receiving signals. All boats 110 in theswarm use the same frequency.

Every broadcast packet may have the same generic structure shown inTable 1. This table shows a sample of the information that might bebroadcast from each of the agents in FIG. 1 within one transmissioncycle, which may have a duration of about 1 second. Each packet containsa vehicle-specific portion (“vehicle data”) and a general portion(“command data”). The vehicle data includes an agent identifier, or,equivalently, a transceiver identifier (which may, for example, be aunique number or character), a position in a universal reference frame(here given by latitude and longitude) and possibly some otherinformation such as a local environmental reading, an indicator of theagent's battery voltage, and an artificial parameter (e.g., an“A-value”, described in further detail below). The command data, whichmay be used to spread information through the group, may be the same forall agents except when it is in the process of being updated asdescribed below, with reference to FIG. 5. The command data may includea time-stamp (or “stamp data”) of when the latest update occurred, acode (or “mode data”) indicating a mode of operation such as “search” or“return home”, and some additional information such as a latitude andlongitude of the “home” location.

The generic packet structure allows each packet to be deciphered by anyother boat 110 within radio transmission range. Each broadcast packetincludes the transmitting boat's distinct identifier (agent identifier)and its GPS coordinates. It may also include some additional parameterssuch as environmental readings, or operational codes. The packet isrelatively small, e.g., about 40 bytes. If a transmission baud rate of250 kbps is used, then a packet may take less than 2 milliseconds tobroadcast.

TABLE 1 Vehicle Data Command Data Agent Latitude Longitude NeighborsEnvironment A-value Battery Time-stamp Mode Latitude Longitude A 37.9545−76.094 12 16.2 110 11.7 12:23:56 GMT [0 1 0] 37.9688 −76.0462 B 37.9545−76.0925 13 16.7 105 10.9 12:23:56 GMT [0 1 0] 37.9688 −76.0462 C37.9545 −76.0915 4 17.3 103 11.2 12:23:56 GMT [0 1 0] 37.9688 −76.0462 D37.954 −76.0905 16 17.6 101 11.2 12:23:56 GMT [0 1 0] 37.9688 −76.0462 E37.9535 −76.0935 6 16 115 11.4 12:23:56 GMT [0 1 0] 37.9688 −76.0462 F37.9535 −76.092 8 16.8 108 11.3 12:23:56 GMT [0 1 0] 37.9688 −76.0462 G37.9535 −76.091 16 17.3 102 11.6 12:23:56 GMT [0 1 0] 37.9688 −76.0462 H37.953 −76.094 13 15.9 120 11.7 12:23:56 GMT [0 1 0] 37.9688 −76.0462 I37.953 −76.0915 7 17 106 10.7 12:23:56 GMT [0 1 0] 37.9688 −76.0462 J37.9525 −76.0945 14 15.8 130 11.5 12:23:56 GMT [0 1 0] 37.9688 −76.0462K 37.9525 −76.093 10 16.1 125 11.4 12:23:56 GMT [0 1 0] 37.9688 −76.0462L 37.9525 −76.092 12 16.2 120 11.1 12:23:56 GMT [0 1 0] 37.9688 −76.0462M 37.9525 −76.091 11 17.1 106 10.9 12:23:56 GMT [0 1 0] 37.9688 −76.0462N 37.9525 −76.09 9 17.4 104 11.3 12:23:56 GMT [0 1 0] 37.9688 −76.0462 O37.952 −76.094 6 15.6 140 10.8 12:23:56 GMT [0 1 0] 37.9688 −76.0462 P37.952 −76.0915 8 16.3 115 11.6 12:23:56 GMT [0 1 0] 37.9688 −76.0462 Q37.952 −76.0905 11 17.2 105 11.3 12:23:56 GMT [0 1 0] 37.9688 −76.0462 R37.9515 −76.0935 15 15.6 160 11.2 12:23:56 GMT [0 1 0] 37.9688 −76.0462S 37.9515 −76.0925 14 15.9 130 10.9 12:23:56 GMT [0 1 0] 37.9688−76.0462 T 37.951 −76.0945 7 15 150 11.1 12:23:56 GMT [0 1 0] 37.9688−76.0462 U 37.951 −76.0915 15 16 110 11.7 12:23:56 GMT [0 1 0] 37.9688−76.0462 V 37.951 −76.0905 13 16.3 105 11.8 12:23:56 GMT [0 1 0] 37.9688−76.0462 W 37.9505 −76.0935 13 15.2 140 11.7 12:23:56 GMT [0 1 0]37.9688 −76.0462 X 37.9505 −76.092 12 15.6 120 10.8 12:23:56 GMT [0 1 0]37.9688 −76.0462 Y 37.95 −76.093 8 15.4 130 11.1 12:23:56 GMT [0 1 0]37.9688 −76.0462 Z 37.95 −76.091 7 15.5 105 11.3 12:23:56 GMT [0 1 0]37.9688 −76.0462

In a simple configuration there may, for example, be a 1 Hz transmissioncycle frequency common to all boats 110 in the swarm. As used herein,the “transmission cycle frequency” is the reciprocal of the transmissioncycle duration. Each boat 110 broadcasts its most up-to-date packetinformation once within each transmission cycle. Rather thantransmitting at a fixed time within each transmission cycle (or“transmission cycle interval”), each boat 110 transmits its packet at arandom time, newly chosen within each transmission cycle, as illustratedin FIG. 2. For example, if the transmission cycle duration is 1 second,then on average the data packet frequency is 1 Hz, but the time betweensuccessive packet transmissions from a particular agent can vary between0 and 2 seconds. As used herein, a “transmission cycle interval” is theinterval of time over which the transmission cycle extends.

FIG. 3 illustrates an example of when packets might be received from sixneighbors within range of an agent. The duration of each packet isgreatly exaggerated in FIG. 3 to demonstrate the effects of packetoverlap. Broadcasts and receptions all occur once per cycle, but arerandomly distributed within each cycle. In cycle 1 there is no packetoverlap. In cycle 2 two incoming packets (D and E) overlap in time. As aresult of this interference, neither packet can be parsed. In cycle 3 apacket (F) cannot be read because it arrives while the broadcast packetis being sent.

As illustrated in FIG. 3, the randomization of the packet transmissiontime within the transmission cycle interval avoids the persistentinterference that could occur if transmissions were regularly timed.

The transmitted radio signals have a limited range, e.g., on the orderof 150 meters, which is much smaller than the extent of the swarm. Thus,due to physical proximity, any one boat is only within radio range of atmost a few hundred neighboring boats. When a boat is not transmitting,it uses its 2.4 GHz antenna to receive the broadcasts from all otherboats within range.

In the case of a group of one hundred boats, all within radio range ofeach other, for example, each boat receives transmissions (or is itselftransmitting) at most 20% of the time (one hundred packets, each havinga duration of 2 milliseconds) within each one-second cycle. As a result,when any boat transmits its own packet there is an 80% chance that itwill not be “talking over” another boat in the group, i.e. there will beno other broadcasts interfering with its transmission. With all boatshaving similar radio traffic, each boat successfully receives about 80%of the broadcast packets every second. Because the transmission scheduleis randomized, the boats achieving successful transmission in onetransmission cycle may be a different, randomly selected subset of theboats achieving successful transmission in any other transmission cycle,so after 2 seconds (two transmission cycles) each boat may have receivedat least one packet from about 1-0.2², or about 96% of the other boats.After 3 seconds the proportion of other boats from which any boat hassuccessfully received a packet is about 1-0.2³ or about 99%.

In a swarm having a static size, a more structured communication systemmay be capable of achieving higher throughput. However, if the swarmsize varies, either as a result of allowing boats to join or leave thegroup or as a result of the changes in the extent of the swarm, astructured system may encounter challenges maintaining synchronizationto prevent persistent interference. The use of cyclic-random operationmay have the effect that any interference is temporary, even, forexample, in a swarm of thousands of agents spread over severalkilometers. The use of cyclic-random operation may also make it possibleto add or remove boats from the swarm without pre-synchronizing themwith the boats already in the swarm.

Self-Adjustment

In a swarm setting, neighboring agents constitute a sort of environment.An agent may have a sense of neighbors, particularly their relativepositions, so it can constantly update its own position within thegroup. In some embodiments this information is provided in the form ofbroadcast packets containing GPS coordinates. The density of neighborsaround any individual in a swarm may be a balance between a density thatis sufficient for neighbors to carry out well-defined swarm algorithmcalculations but not so great that there is excessive radiointerference.

In some swarm settings the density may be too small or too great. Forexample, when deploying or retrieving a swarm, the density of agents maybe very high, potentially causing excessive radio interference (fromoverlapping packets) which if not remedied could result in each agent'shaving insufficient information about the neighbor environment.Conversely, if the density is small, the bandwidth may be underutilized.

It is possible to devise an adjustment scheme, using cyclic-randomcommunication, that meets the conditions of being fully scalable,rapidly adaptive, and not reliant on any forced communicationcoordination between agents. The statistical reliability of thecyclic-random communication system lets agents self-adjust theirtransmission cycle duration in a way that results in high throughput inthe group as a whole.

Within a swarm the basic goal may be for each agent to obtain as muchcurrent information about its neighbors as possible. Because packets arecoming in at random from all neighbors this is equivalent to the goalthat each agent successfully receive as many packets per second aspossible. The number of successfully received packets per second isreferred to herein as the “successful packet rate”, or, as mentionedabove, “throughput”.

FIG. 4 is a graph of throughput as a function of local population size(number of neighbors within range), for four different transmissioncycle frequencies: 1 Hz (curve 410), 2 Hz (curve 420), 4 Hz (curve 430),and 8 Hz (curve 440). The four curves show the number of packets thatare successfully received by a single agent per unit time (throughput).The curves are constructed experimentally by averaging the results fromseveral computer-simulated trials for different transmission rates (1Hz=1.0 second cycle duration, 2 Hz=0.5 second cycle duration, 4 Hz=0.25second cycle duration, 8 Hz=0.125 second cycle duration) and for groupsof different sizes. In these simulations the packet duration is twomilliseconds. As shown in FIG. 4, for each transmission rate there is amaximum rate of clear packets received per second (about 75). Thismaximum throughput corresponds to a particular number of neighborswithin communication range.

FIG. 4 shows that for a given packet duration and transmission cycleduration there is a particular local population size (number ofneighbors within range) that results in the greatest throughput. For apacket duration of 2 milliseconds the greatest throughput is about 75packets per second, regardless of which of the four differenttransmission cycle frequencies is used. The transmission cycle frequencyat which the greatest throughput is achieved depends on the number ofneighbors. Thus, in some embodiments an agent self-adjusts itstransmission cycle frequency by noting its neighbor count and adjustingits transmission cycle frequency using the following equation:

transmission cycle frequency=0.4/(number of neighbors*packet duration),

where the transmission cycle frequency has units of cycles per secondand the packet duration has units of seconds. If all agents set theirown transmission cycle frequency in real time according to thisequation, the total throughput for the swarm of agents may be maximizedwithout the agents having to coordinate between themselves. In someembodiments a factor different from 0.4 (e.g., a factor in the rangebetween 0.1 and 4.0) is used instead of the factor of 0.4 in theequation above.

In a region of a swarm in which the density of agents is not uniform, anadditional improvement to this method for adjusting the transmissioncycle frequency may be achieved if one of the pieces of information thatneighbors share is the number of neighbors they are receiving signalsfrom. Sharing this information may avoid a situation in which a firstagent, which has few neighbors, transmits at a high transmission cyclefrequency and thereby causes excessive interference to a second agent,which is a neighbor of the first agent and which has many neighbors. Insuch a situation it may be that a lower transmission cycle frequencyfrom the first agent would result in a higher throughput for the secondagent.

The number of neighbors from which an agent is receiving packets may beincluded in the agent's broadcast packet. With this information, eachagent can calculate the average “crowding” (i.e., neighbor count) of thepopulation into which its outgoing packet will be broadcast, and it mayadjust its transmission cycle frequency to maximize throughput in thegroup. A similar equation may be used by a first agent to adjust itstransmission cycle frequency, in this case:

transmission cycle frequency=0.4/(average neighbor count overneighbors*packet duration)

where the transmission cycle frequency has units of cycles per secondand the packet duration has units of seconds, and where the averageneighbor count over neighbors is the average of the neighbor counts ofall of the agents that are neighbors of the first agent. A “neighborcount” of an agent, as used herein, refers to the number of agentslisted in a neighbor list maintained by the agent (as described infurther detail below). In some embodiments a factor different from 0.4(e.g., a factor in the range between 0.1 and 4.0) is used instead of thefactor of 0.4 in the equation above.

Neighbor List

As mentioned above, each agent in a swarm may be aware of its closeneighbors and constantly update its own behavior (e.g. its owngeographic location or its spatial relationship within the group) basedon a swarm algorithm calculation that uses vectors describing therelative positions of neighbors. Each agent may have concurrent orsimultaneous awareness of all of its neighboring agents. Each agent maymaintain a list of relative positions and possibly other neighborinformation such as environmental readings or velocity vectors.

When all of this neighbor information is received in the form ofdiscrete radio packets broadcast at different times, some of which maybe lost due to interference or fluctuating link loss, an agent'sawareness of its neighbors may be imperfect, e.g., delayed for at leastsome neighbors. A neighbor list, which may be maintained by the agent tobe as complete and current as possible, may be employed to mitigate someof these effects.

The neighbor list may be constructed using the ID numbers and GPScoordinates gleaned from neighbor packet broadcasts. Construction of theneighbor list is based on the observation that agents in a real swarm,such as robotic boats on the ocean surface, may have a persistentphysical presence and any significant change in their position generallyoccurs much more slowly than the packet transmission rate, e.g. 1 Hz. Asa result, if in one one-second window a neighbor's location is discernedfrom the GPS data in its packet, it can be reasonably assumed that thatneighbor is still there during the next second even though its nexttransmitted packet may have been missed. However, with each passingsecond during which additional packets from a neighbor are expected butnot received, the reliability of its position decreases.

In one embodiment a neighbor list is created by adding agents to thelist when packets are received, updating the information for each agentwhenever a new packet is received from it, and dropping an agent fromthe list after a certain time (referred to as a “persistence duration”)has elapsed without a new packet. Table 2 shows the evolution of such aneighbor list in one embodiment, for a first agent having sevenneighbors (identified by letters, e.g., “O”, “K”, “S”, etc.), from eachof which it has just received a packet, in cycle 1. In cycle 2, newpackets are received from agents O, K, W, J, and Y, but not from agentsS and T. The same occurs in cycle 3. Also, in cycle 3, the first agentreceives a packet from agent H and adds agent H to the neighbor list. Incycle 4 a counter is reset when an updated packet from agent S isreceived. At the end of cycle 6, not having received a packet from agentT in five consecutive cycles, which may correspond to the persistenceduration, the first agent removes agent T from the neighbor list.

TABLE 2 Cycle 1 Cycle 2 Cycle 3 Cycle 4 Cycle 5 Cycle 6 cycles cyclescycles cycles cycles cycles Neighbor since new NeighBor since newNeighbor since new Neighbor since new Neighbor since new Neighbor sincenew ID packet ID packet ID packet ID packet ID packet ID packet O 0 O 0O 0 O 0 O 1 O 2 K 0 K 0 K 0 K 0 K 0 K 0 S 0 S 1 S 2 S 0 S 0 S 0 W 0 W 0W 0 W 0 W 0 W 0 T 0 T 1 T 2 T 3 T 4 J 0 J 0 J 0 J 0 J 0 J 0 Y 0 Y 0 Y 0Y 0 Y 0 Y 0 H 0 H 0 H 0 H 0 T is dropped H is added S is restarted

In another embodiment, when a new packet is not received from aneighbor, the relative coordinates of that neighbor are updated (or theabsolute position is updated) with each cycle, to reflect the expectedmotion of the neighbor, either using the last broadcast velocity vector,or using an estimated velocity calculated from position changes recordedfrom the last 2 or 3 received packets.

In some embodiments, the persistence duration is longer than the cycleduration. If the persistence is too short (e.g. less than 2 cycles) theneighbor list may be incomplete. If the persistence is too long (e.g.greater than 10 cycles), much of the information about neighbors in thelist may not be sufficiently accurate or reliable to be of value for aswarm calculation.

The neighbor list may be an internal representation, in each agent, ofall the information it has about its neighbors, including, e.g.,information about the positions and respective environments of itsneighbors. As such, each agent may use the neighbor list, for example,to compute navigation vectors from swarm calculations, or to make anyother assessment of the environment of neighbors. Further, as mentionedabove, the neighbor count may be determined by counting the number ofneighbors on the neighbor list; this number may be included in theagent's broadcast packet to assist other agents with their transmissioncycle frequency calculations.

Command Data

Agents in a swarm that are not within range of each other are not indirect contact with each other, and, in some circumstances there may beno central controller that is in direct communication with all agentssimultaneously. It may however be desirable or advantageous for anoperator, or a single agent in the group, to be able to send a commandto the entire group, such as a directive to change behavioral modes from“search” to “converge” or from “standard operation” to “emergency stop”.Since inter-agent communication is local, not global, a second portionof the packet may be defined that includes information that is repeatedfrom agent to agent.

This Command Data portion of each packet may include two key elements.First it may include a byte or a few bits that identify a “mode”. Forexample [001] might identify “normal swarm behavior”, [010] couldidentify “converge on a specified geographic location”, [111] couldidentify “emergency stop”. Supporting information, such as a specificGPS location, may also be included in this global portion of a packet.Second there may be another segment of the packet (“stamp data”) that isa member of an ordered list, e.g., it may be a serial count (stamp) ofevery operator command, or a time stamp in a global frame (such as GMTmonitored from the GPS signal) of when a command is given. As usedherein, values that are “members of an ordered list” are ones for whichit is possible for a transceiver to determine which of two such valuesprecedes the other (i.e., is earlier in the ordered list than theother). A monotonically increasing list of numbers (such as a sequenceof time stamps) is an example of an ordered list, as is a monotonicallydecreasing list of numbers.

FIG. 5 is a flowchart of a method for handling command data, in oneembodiment. The command data may include information to be repeated insuccessive transmissions, such as a general command or a mode that is tobe propagated throughout the swarm. The vehicle data may include themost current information specific to the agent transmitting the packet,such as the agent's current location, velocity or latest environmentalreading. During each cycle, the agent executes a receiving/updating loop510, for each received packet, as follows. When the agent receives a newpacket it compares the stamp in that packet with the stamp of itscurrent mode. If the stamp is the same or older the agent stays in itscurrent mode and broadcasts its existing stamp and mode in its outgoingpacket. If the stamp is newer the agent begins operating in the modeassociated with the newer stamp, updates, in an act 520, the vehicledata portion of the packet, and broadcasts, in an act 530, the newerstamp and mode in the command data portion of its outgoing packet,together with the vehicle data portion. As such, the agent operates onthe basis of the most up-to-date mode.

In such an embodiment, when an operator sends a command that is onlyreceived by a single agent or by a few agents, the command may rapidlydisseminate through the swarm. Also, a second operator, out ofcommunication with the first, may change the mode. Further, an agent mayalso be the initiator of a new global command. For example, if the swarmis in “search” mode where it is widely spread out and monitoring for theping from a black box, then when one agent senses the box, it canbroadcast its GPS coordinates along with a new “converge” command so allagents move toward the target location (e.g., toward the agent thatsensed the box or toward the inferred location of the box).

Because the self-adjustment of transmission cycle frequency describedabove maximizes the packet communication rate within the swarm, it alsomaximizes the speed with which command data disseminates through thegroup.

Artificial Topography

As mentioned above, environmental readings, such as water temperature,can be broadcast in packets. With several such readings tied toneighbors' geographic locations, it is possible for agents to calculategradients in the environment around them. This sort of distributedsensing is one of the powerful capabilities of a robotic swarm. Thesegradients may be used to influence the motive vector of each agent, andthe sum result may be a swarm that migrates very effectively up or downregional environmental gradients.

The packet broadcast system also provides a medium for an artificialtopography that may be used as a global pointer within the distributedswarm, as described in further detail in the '224 Application. Forexample, as illustrated in FIG. 6, each agent may maintain two parametervalues, a private A-value, and a public A-value, the latter of which istransmitted with each packet transmitted by the agent. During eachtransmission cycle, each agent recalculates its public A-value as theaverage of (i) the A-values it has received from its neighbors and (ii)its private A-value (and then includes the recalculated public A-valuein the next packet it transmits). FIG. 6 shows exemplary values of thepublic A-value (below each agent) and the private A-value (below eachagent, in parentheses).

In operation, if all agents have the same private value, e.g. 100, thenall averaged A-values are 100 and all of the public A-values are 100. Inthis scenario there is no gradient in the spatial distribution ofA-values and they form a flat topography. However, if one agent isassigned a different private A-value, e.g. 200, (this value being, e.g.,self-assigned as a result of the agent's detecting an anomaly orintentionally assigned by an operator), then the averaging andbroadcasting process forms a gradient in the public A-values slopingfrom that one agent outwards.

This topography, generated entirely by the local communication system,forms a robust regional gradient pointing toward the agent of interest.The averaging process diffuses the gradient across the swarm, and evenremote agents can detect the direction toward the agent with the largerprivate A-value. This directionality may be used in action decisions byevery agent, for example to converge on the location of the agent withthe larger private A-value, without needing a direct or quantitativereading from the agent with the larger private A-value.

Because the self-adjustment described earlier in this document maximizesthe packet communication rate within the swarm, it therefore maximizesthe speed with which the topographic gradient disseminates and smoothsitself. The self-adjustment improves the formation of a consistent,reliable gradient that can be a useful swarm management tool.

Sniffer

In some embodiments, swarming is based on short-range communication, andit may be challenging for an operator to obtain information from distantagents. In some distributed systems, remote information is transmittedthrough a chain of intermediaries. This is technologically challengingin a dynamic network, and may be slow because information from distantagents may be relayed by a large number of intermediaries, and becauseall of the information conveyed to the operator may pass through a smallnumber of agents in a neighborhood of the operator, which may form abottleneck. In some embodiments, an open broadcast system as describedherein lends itself to a different method that is flexible and imposesrelatively little delay.

In one embodiment, illustrated in FIG. 7, the operator makes use of a“sniffer” including a high-gain directional antenna 710 (e.g., anantenna having a gain of at least 5 dBi , i.e., a gain of at least 5 dBrelative to that of a hypothetical isotropic antenna pattern) attachedto a graphic display screen 720. Together these elements comprise a“sniffer” that can observe the swarm without needing to co-opt thecommunication channels. A directional antenna 710 may be capable ofreceiving signals from agents that are considerably more distant thanagents from which an omnidirectional antenna (such as theomnidirectional antennas that may be on the agents themselves) would becapable of receiving signals. If it is handheld or on a pivoting mountthe antenna 710 may be scanned across the swarm to receive allinformation available in the broadcast packets. The sniffer receivescomplete packet information so it may discern locations and otherrelevant data, such as environmental readings. This information may beplotted on the display screen 720 dynamically, in near real time. If theminimum transmission cycle frequency within the swarm is sufficientlyhigh, it may be possible to sweep the sniffer antenna 710 across theswarm at a relatively high rate (e.g., at 10 degrees per second) andnonetheless capture, during the sweep, at least one transmitted packetfrom each agent.

Monitoring the swarm through a sniffer may impose no additional burdenon the swarm communication system, and the broadcast information isavailable to other operators or other agents. For example, asillustrated in FIG. 8, an aerial drone 810 may be stationed over anocean surface swarm, where it may gather information from the entireswarm and transmit it to the operator from its higher vantage point.

Radio packets broadcast by the agents may be configured to includeadditional information that an operator may want to monitor. Forexample, packets may include information about swarm health, such as thebattery level of each agent. In another embodiment packets may includeinformation recorded when the swarm was not in range of the sniffer,such as water temperature readings recorded while an agent wassubmerged. As long as the information can be expressed in a few dozenbytes, it may be included in the swarm packet without compromising theoverall communication system.

Swarm Device

Various robotic vehicles with advanced capabilities for autonomousnavigation in real-world settings, such as aerial drones flying throughthe built environment, or self-driving cars navigating public roadways,may benefit from the features of the communication system describedherein. In some cases, these vehicles may operate amongst crowds ofother such vehicles, either to make a swarm or just to navigate smoothlyin traffic. In these cases, a device incorporating these features, thatmay readily be attached to a robotic vehicle 920, may be used to givethe robotic vehicle 920 up-to-date awareness of neighbors and theability to swarm.

FIG. 9 illustrates a schematic of a swarm device 910 that can be addedto an existing autonomous vehicle 920. The swarm device 910 includes aradio system and a microprocessor. The microprocessor performs thefollowing functions:

1. It maintains a neighbor list. The processor stores relevantinformation from each neighbor, updating with the latest data andremoving neighbors that have not been heard from within a specifiedpersistence duration.

2. If the swarm is scalable, it automatically adjusts its transmissioncycle duration based on information from neighbors about the amount ofradio crowding in the area.

3. It receives and sends packets to the radio. It may decode thereceived packets and use them to update the neighbor list. It may takedata from the vehicle (GPS, environmental readings, etc.) to create thevehicle data portion of a packet, and it may use command data fromneighbors to update the command data to include in the outgoing packet.

4. It queries the autopilot for the latest vehicle dynamic information(e.g. location, velocity, etc.) that will be used in swarm calculations.

5. It provides the vehicle autopilot with information in the neighborlist, such as command data, which may be used to alter behavioral modes.

Equipped with this device, the vehicle 920 may be well-informed aboutthe state of the neighboring vehicles 920 around it, and the autopilotmay be able to use this information for navigation. For example, someautonomous vehicles 920 are equipped with collision avoidance behaviorswhere the vehicle 920 reacts to keep a safe distance from sensedobstructions. The swarm device 910 can be incorporated as an additionalobstruction sensor, alerting the vehicle 920 to the proximity of othervehicles 920 (that are broadcasting suitable packets) that may bedifficult to sense with computer vision, radar or other on-boardequipment.

In another embodiment the attached swarm device 910 may carry out itsown swarm processing. Using a swarm algorithm, such as one that seeks tomaintain a consistent spacing from neighbors, the microprocessor maycalculate a commanded velocity vector (having a direction (the commandeddirection) and a magnitude (the commanded speed)) for the vehicle 920 totravel to maintain an ideal relative position within the group. Thissimple vector may then be the only information that is passed to thevehicle's autopilot.

In another embodiment the device attached to the vehicle 920 may beconfigured primarily to maximize the ability for a sniffer to monitorvehicles 920 in a group, without regard for coordinated swarmingbehavior. In such an embodiment, the primary purpose for attaching thedevice to a population of vehicles 920 may be simply to monitor thepopulation, and the device's self-adjustment of the transmission cycleduration helps assure that a sniffer can glean the most information fromthe group even as the population density varies.

Other Embodiments

Some embodiments described herein are directed a single swarm ofvehicles all communicating on a single frequency (and single channel).It should be understood that the value of the inventions is not limitedto such embodiments.

Depending on bandwidth requirements it may be desirable or advantageousto use multiple frequencies, or multiple channels on the same frequency,to enable a larger number of agents to broadcast data withoutunacceptable interference.

Some embodiments of the communication system may be particularlyvaluable in any system comprising a large number of agents, whether theyform one swarm or not. The rapidly updated broadcasts may allow anyagent to be in near-constant contact with any other agent broadcastingenough information for coordinated behavior. This may be relevant forapplications such as self-driving cars or delivery drones. In thesesituations, there may potentially be millions of vehicles, any one ofwhich could come near any other at any time. Pre-establishedcommunication links may be too limiting for this number of potentialconnections. The open broadcast system described in this document allowsany vehicle within radio range be detected and assessed by any otherwithin a second or two. This may be useful to expand the range ofcoordinated interaction beyond the on-board sensing (e.g., computervision, radar, laser) that such vehicles may be equipped with.

Although for purposes of illustrations some embodiments described hereinemploy radio transceivers, in other embodiments communications areotherwise established, e.g., using sound waves propagating in water orin air. As used herein, unless otherwise specified, two agents areneighbors (of each other) if and only if they are within communicationrange of each other. Unless otherwise specified, two agents are withincommunication range of each other if and only if in the absence ofinterference at least 10% of the packets transmitted by one agent aresuccessfully received by the other agent. Although for simplicity someembodiments are described for transceivers having symmetric rangerelationships (i.e., a first transceiver is within range of thetransmissions of a second transceiver if and only if the secondtransceiver is within range of the transmissions of a first transceiver)the invention is not limited to such situations and may readily beemployed in embodiments in which the range relationships are notsymmetric, e.g., in which some transceivers transmit with higher powerthan others.

In view of the foregoing, some embodiments provide a swarm communicationsystem. Each of a plurality of transceivers determines a transmissioncycle duration, and transmits one packet per transmission cycle, eachpacket being transmitted at a random point in time within thetransmission cycle. The duration of the transmission cycle of a firsttransceiver may be adjusted according to the number of othertransceivers within range of the first transceiver, or according to thenumber of other transmitters within range of each of the othertransmitters that are within range of the first transceiver.

Data processing functions may be performed, in the agent and/or in thetransceiver, by a processing circuit. The term “processing circuit” isused herein to mean any combination of hardware, firmware, and software,employed to process data or digital signals. Processing circuit hardwaremay include, for example, application specific integrated circuits(ASICs), general purpose or special purpose central processing units(CPUs), digital signal processors (DSPs), graphics processing units(GPUs), and programmable logic devices such as field programmable gatearrays (FPGAs). In a processing circuit, as used herein, each functionis performed either by hardware configured, i.e., hard-wired, to performthat function, or by more general purpose hardware, such as a CPU,configured to execute instructions stored in a non-transitory storagemedium. A processing circuit may be fabricated on a single printedcircuit board (PCB) or distributed over several interconnected PCBs. Aprocessing circuit may contain other processing circuits; for example aprocessing circuit may include two processing circuits, an FPGA and aCPU, interconnected on a PCB.

It will be understood that, although the terms “first”, “second”,“third”, etc., may be used herein to describe various elements,components, regions, layers and/or sections, these elements, components,regions, layers and/or sections should not be limited by these terms.These terms are only used to distinguish one element, component, region,layer or section from another element, component, region, layer orsection. Thus, a first element, component, region, layer or sectiondiscussed herein could be termed a second element, component, region,layer or section, without departing from the spirit and scope of theinventive concept.

Spatially relative terms, such as “beneath”, “below”, “lower”, “under”,“above”, “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. It will beunderstood that such spatially relative terms are intended to encompassdifferent orientations of the device in use or in operation, in additionto the orientation depicted in the figures. For example, if the devicein the figures is turned over, elements described as “below” or“beneath” or “under” other elements or features would then be oriented“above” the other elements or features. Thus, the example terms “below”and “under” can encompass both an orientation of above and below. Thedevice may be otherwise oriented (e.g., rotated 90 degrees or at otherorientations) and the spatially relative descriptors used herein shouldbe interpreted accordingly. In addition, it will also be understood thatwhen a layer is referred to as being “between” two layers, it can be theonly layer between the two layers, or one or more intervening layers mayalso be present.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the inventiveconcept. As used herein, the terms “substantially,” “about,” and similarterms are used as terms of approximation and not as terms of degree, andare intended to account for the inherent deviations in measured orcalculated values that would be recognized by those of ordinary skill inthe art. As used herein, the term “major component” refers to acomponent that is present in a composition, polymer, or product in anamount greater than an amount of any other single component in thecomposition or product. In contrast, the term “primary component” refersto a component that makes up at least 50% by weight or more of thecomposition, polymer, or product. As used herein, the term “majorportion”, when applied to a plurality of items, means at least half ofthe items.

As used herein, the singular forms “a” and “an” are intended to includethe plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising”, when used in this specification, specify thepresence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof. As used herein, the term “and/or”includes any and all combinations of one or more of the associatedlisted items. Expressions such as “at least one of,” when preceding alist of elements, modify the entire list of elements and do not modifythe individual elements of the list. Further, the use of “may” whendescribing embodiments of the inventive concept refers to “one or moreembodiments of the present invention”. Also, the term “exemplary” isintended to refer to an example or illustration. As used herein, theterms “use,” “using,” and “used” may be considered synonymous with theterms “utilize,” “utilizing,” and “utilized,” respectively.

It will be understood that when an element or layer is referred to asbeing “on”, “connected to”, “coupled to”, or “adjacent to” anotherelement or layer, it may be directly on, connected to, coupled to, oradjacent to the other element or layer, or one or more interveningelements or layers may be present. In contrast, when an element or layeris referred to as being “directly on”, “directly connected to”,“directly coupled to”, or “immediately adjacent to” another element orlayer, there are no intervening elements or layers present.

Any numerical range recited herein is intended to include all sub-rangesof the same numerical precision subsumed within the recited range. Forexample, a range of “1.0 to 10.0” is intended to include all subrangesbetween (and including) the recited minimum value of 1.0 and the recitedmaximum value of 10.0, that is, having a minimum value equal to orgreater than 1.0 and a maximum value equal to or less than 10.0, suchas, for example, 2.4 to 7.6. Any maximum numerical limitation recitedherein is intended to include all lower numerical limitations subsumedtherein and any minimum numerical limitation recited in thisspecification is intended to include all higher numerical limitationssubsumed therein.

Although exemplary embodiments of a swarm communication method anddevice have been specifically described and illustrated herein, manymodifications and variations will be apparent to those skilled in theart. Accordingly, it is to be understood that a swarm communicationmethod and device constructed according to principles of this inventionmay be embodied other than as specifically described herein. Theinvention is also defined in the following claims, and equivalentsthereof.

What is claimed is:
 1. A method for communicating between a plurality oftransceivers, the method comprising: establishing, by a firsttransceiver of the plurality of transceivers, a first transmission cycleinterval having a duration; and transmitting, during the firsttransmission cycle interval, by the first transceiver, a packet, theposition in time of the packet within the first transmission cycleinterval being randomly selected, the establishing of the firsttransmission cycle interval comprising selecting the duration of thefirst transmission cycle interval based on: for each of a plurality ofsecond transceivers, a count of transceivers within communication rangeof that second transceiver, the plurality of second transceivers being asubset of the plurality of transceivers, each of the second transceiversbeing within communication range of the first transceiver.
 2. The methodof claim 1, further comprising determining, by a second transceiver ofthe plurality of second transceivers, the count of transceivers withincommunication range of that second transceiver by: during a first timeinterval having a duration of k transmission cycles of that secondtransceiver, k being a whole number greater than 2: receiving aplurality of packets; and adding, to a list of transceivers identifiers,a received transceiver identifier when the received transceiveridentifier is not already in the list, removing, from the list eachtransceiver identifier not in any packet of the plurality of packets;and counting the number of transceiver identifiers in the list.
 3. Themethod of claim 1, wherein the selecting of the duration of the firsttransmission cycle interval comprises calculating the duration of thefirst transmission cycle interval to be proportional to an average, overthe plurality of second transceivers, of the respective count oftransceivers within communication range of each of the secondtransceivers.
 4. The method of claim 3, wherein the selecting of theduration of the first transmission cycle interval comprises calculatingthe duration D of the first transmission cycle interval according to theequationD=N*T/B wherein N is the average, over the plurality of secondtransceivers, of the respective count of transceivers withincommunication range of each of the second transceivers, T is a durationof the packet, and B is a constant having a value between 0.1 and 4.0.5. The method of claim 1, further comprising: receiving, by the firsttransceiver, a packet comprising received stamp data and received modedata, the stamp data being a member of an ordered list; and when thereceived stamp data is later in the ordered list than stored stamp datain the first transceiver, overwriting the stored stamp data with thereceived stamp data, and overwriting stored mode data in the firsttransceiver with the received mode data; and when the received stampdata is not later in the ordered list than the stored stamp data in thefirst transceiver, leaving the stored stamp data and stored mode dataunchanged.
 6. A method for communicating between a plurality oftransceivers, the method comprising: establishing, by a firsttransceiver of the plurality of transceivers, a first transmission cycleinterval having a duration; and transmitting, during the firsttransmission cycle interval, by the first transceiver, a packet, theposition in time of the packet within the first transmission cycleinterval being randomly selected, the establishing of the firsttransmission cycle interval comprising selecting the duration of thefirst transmission cycle interval based on a count of transceiverswithin communication range of the first transceiver.
 7. The method ofclaim 6, wherein the selecting of the duration of the first transmissioncycle interval comprises calculating the duration of the firsttransmission cycle interval to be proportional to the count oftransceivers within communication range of the first transceiver.
 8. Themethod of claim 7, wherein the selecting of the duration of the firsttransmission cycle interval comprises calculating the duration D of thefirst transmission cycle interval according to the equationD=N*T/B wherein N is the count of transceivers within communicationrange of the first transceiver, T is a duration of the packet, and B isa constant having a value between 0.1 and 4.0.
 9. The method of claim 6,further comprising: receiving, by the first transceiver, a packetcomprising received stamp data and received mode data, the stamp databeing a member of an ordered list; and when the received stamp data islater in the ordered list than stored stamp data in the firsttransceiver, overwriting the stored stamp data with the received stampdata, and overwriting stored mode data in the first transceiver with thereceived mode data; and when the received stamp data is not later in theordered list than the stored stamp data in the first transceiver,leaving the stored stamp data and stored mode data unchanged.
 10. Asystem, comprising: a plurality of spatially separated agents, eachagent comprising a respective transceiver of a corresponding pluralityof transceivers, a first transceiver of the plurality of transceiversbeing configured to: establish a first transmission cycle intervalhaving a duration; and transmit, during the first transmission cycleinterval, by the first transceiver, a packet, the position in time ofthe packet within the first transmission cycle interval being randomlyselected, the establishing of the first transmission cycle intervalcomprising selecting the duration of the first transmission cycleinterval based on: a count of transceivers within communication range ofthe first transceiver; or for each of a plurality of secondtransceivers, a count of transceivers within communication range of thatsecond transceiver, the plurality of second transceivers being a subsetof the plurality of transceivers, each of the second transceivers beingwithin communication range of the first transceiver.
 11. The system ofclaim 10, further comprising determining, by a second transceiver of theplurality of second transceivers, the count of transceivers withincommunication range of that second transceiver by: during a first timeinterval having a duration of k transmission cycles of that secondtransceiver, k being a whole number greater than 2: receiving aplurality of packets; and adding, to a list of transceivers identifiers,a received transceiver identifier when the received transceiveridentifier is not already in the list, removing, from the list eachtransceiver identifier not in any packet of the plurality of packets;and counting the number of transceiver identifiers in the list.
 12. Thesystem of claim 10, wherein the selecting of the duration of the firsttransmission cycle interval comprises calculating the duration of thefirst transmission cycle interval to be proportional to the count oftransceivers within communication range of the first transceiver. 13.The system of claim 12, wherein the selecting of the duration of thefirst transmission cycle interval comprises calculating the duration Dof the first transmission cycle interval according to the equationD=N*T/B wherein N is the count of transceivers within communicationrange of the first transceiver, T is a duration of the packet, and B isa constant having a value between 0.1 and 4.0.
 14. The system of claim10, wherein the selecting of the duration of the first transmissioncycle interval comprises calculating the duration of the firsttransmission cycle interval to be proportional to an average, over theplurality of second transceivers, of the respective count oftransceivers within communication range of each of the secondtransceivers.
 15. The system of claim 14, wherein the selecting of theduration of the first transmission cycle interval comprises calculatingthe duration D of the first transmission cycle interval according to theequationD=N*T/B wherein N is the average, over the plurality of secondtransceivers, of the respective count of transceivers withincommunication range of each of the second transceivers, T is a durationof the packet, and B is a constant having a value between 0.1 and 4.0.16. The system of claim 10, further comprising: receiving, by the firsttransceiver, a packet comprising received stamp data and received modedata, the stamp data being a member of an ordered list; and when thereceived stamp data is later in the ordered list than stored stamp datain the first transceiver, overwriting the stored stamp data with thereceived stamp data, and overwriting stored mode data in the firsttransceiver with the received mode data; and when the received stampdata is not later in the ordered list than the stored stamp data in thefirst transceiver, leaving the stored stamp data and stored mode dataunchanged.
 17. The system of claim 10, further comprising a sniffercomprising a directional antenna, having a gain, in one direction, of atleast 5 dBi.
 18. A system for providing communications to a swarm ofvehicles, the system comprising a plurality of transceivers, a firsttransceiver of the plurality of transceivers being configured to: bemechanically and electrically connected to a vehicle; establish a firsttransmission cycle interval having a duration; and transmit, during thefirst transmission cycle interval, by the first transceiver, a packet,the position in time of the packet within the first transmission cycleinterval being randomly selected, the establishing of the firsttransmission cycle interval comprising selecting the duration of thefirst transmission cycle interval based on: a count of transceiverswithin communication range of the first transceiver; or for each of aplurality of second transceivers, a count of transceivers withincommunication range of that second transceiver, the plurality of secondtransceivers being a subset of the plurality of transceivers, each ofthe second transceivers being within communication range of the firsttransceiver.
 19. The system of claim 18, wherein the first transceiveris configured to send, to the vehicle, information about the location ofother nearby transceivers of the plurality of transceivers.
 20. Thesystem of claim 18, wherein the first transceiver is configured to send,to the vehicle, a commanded velocity vector.